1. Field of the Invention
The present invention relates to a one side surface molten metallic coating method for coating on one side only of a continuous metal.
2. Description of the Prior Art
It has been developed to use strips coated on one side only which are prepared by coating a molten metal on one side only to improve anticorrosive and soldering characteristics and which are used in the cars and household electric instruments etc.
An electric plating process has been known as the process for preparing a strip of metal coated on one side only. In the electric plating process, the productivity is low and the cost is high in order to prepare a sheet or strip of metal on which a large amount of molten metal is coated. Moreover, the process could not be applied for coating aluminum etc.
On the contrary, if a hot dipping process for coating a strip of metal by immersing it in a molten metal bath, can be applied on one side only, the advantages are remarkable from the economical and technical viewpoints. Various processors have been proposed.
U.S. Pat. No. 3,149,987 and U.S. Pat. No. 3,121,019 disclose the processes for coating on one side only by coating sodium bentonite or an alkaline earth hydroxide on a rear surface to form a coating and immersing it in a molten metal bath and then, removing the coating of sodium bentonite or an alkaline earth hydroxide. These processes include the step of coating a resist on the rear surface and the step of removing the resist after the molten metallic coating whereby the processes are remarkably complicated and the resist coated on the rear surface contaminates the molten metal bath and the contaminated molten metal is coated to cause a trouble.
U.S. Pat. No. 4,082,868 and U.S. Pat. No. 4,114,563 disclose the process for coating a molten metal on one side surface of a strip by placing a deflector roll near a bath surface to form meniscus by a surface tension of a molten metal between the strip passing the roll and the molten metal surface.
In the process, the surface tension of the molten metal is utilized, and accordingly, a gap between the molten metal surface and the strip should be precisely maintained. Thus, the edge of the strip has a strain in itself whereby a distance to the molten metal surface is varied by vibration caused by the running thereby causing disadvantages of a partial uncoated surface or a wraparound of a molten metal from an edge to the opposite surface.